This invention is directed to a method and apparatus for the production of solar cells whereby adjacent layers of amorphous semiconductor material of differing conductivity types are deposited in separate dedicated glow discharge chambers.
Photovoltaic devices are known as structure by which solar radiation can be converted into useable electrical energy. One of the known devices in this class is a silicon solar cell which has a multi-layered, doped body of amorphous silicon. Such a silicon solar cell and the process of successive deposition of doped layers within a glow discharge chamber to build up the solar cell structure is described in U.S. Pat. No. 4,226,898, Stanford R. Ovshinsky and Arun Madan, issued from U.S. patent application Ser. No. 887,353, filed Mar. 16, 1978 for AMORPHOUS SEMICONDUCTORS EQUIVALENT TO CRYSTALLINE SEMICONDUCTORS PRODUCED BY A GLOW DISCHARGE PROCESS. The patent disclosure of which is incorporated into this disclosure in its entirety. This patent teaches the formation of the various doped and intrinsic layers of amorphous material in a single vacuum chamber within a housing. Conduits allow the successive admission of various reaction gas mixtures both containing various dopants (in the production of doped layers), and free of dopants (in the production of intrinsic material.)
With the batch-processing in a single chamber, the optimization and manufacturing speed of the finished structure device cells is more restricted than desired. The production of multilayer devices including adjacent layers of differing material types (including intrinsic layers) when performed in a single glow discharge chamber requires complex control apparatus and time consuming techniques. In particular, the initializing of the vacuum and substrate temperature for each device and cooling following the deposition of the device layers greatly lengthens the average device fabrication time.
Further, the contamination of the different material type layers, especially the intrinsic layer, with undesired process or other elements must be avoided for optimum device function. In a single chamber process, this requires added intermediate evacuation steps to avoid cross contamination.